Work will continue on the decay and processing of RNA in Escherichia coli. This work will concentrate on the enzymes ribonuclease II, ribonuclease III, ribonuclease H, ribonuclease M, ribonuclease N, and ribonuclease R. Some of these enzymes, especially ribonuclease M and RNN, which are new enzymes discovered in our laboratory would be further purified and characterized. Mutant strains deficient in the enzymes, ribonuclease I, II, III, and polynucleotide phosphorylase would be constructed in various combinations, and their physiological properties would be studied with respect to RNA metabolism post-transcription i.e., processing and decay. We shall concentrate on studying mutants in RNase III and their revertants. In processing we shall continue to study mainly, the biosynthesis of ribosomal RNA and in decay, we shall study mainly the fate of mRNA and rRNA. BIBLIOGRAPHIC REFERENCES: Apirion, D., Neil, J., and Watson, N. Consequences of losing ribonuclease III on the Escherichia coli. Mol. Gen. Genetics (in press, 1976). Saltzman, L., and Apirion, D. Binding of erythromycin to the 50S ribosomal subunit is affected by alterations in the 30S ribosomal subunit. Mol. Gen. Genetics (in press, 1976).